As wireless communications standards continue to evolve to provide improvements in data rates and reliability, increasingly stringent requirements are placed on the radio frequency (RF) power amplifiers (PAs) used to transmit wireless signals. RF PAs compliant with the latest wireless communication standards must provide a high degree of linearity and a large gain over a wide bandwidth, while simultaneously being highly efficient in order to preserve the battery life of a mobile terminal in which they are incorporated. Silicon (Si) and gallium arsenide (GaAs) RF PAs are well known and widely used, yet suffer from a relatively narrow bandwidth and a limited output power, characteristics which are inherent in the devices due to the narrow band-gap of their respective material systems. In order to improve the performance of a mobile terminal, wide band-gap semiconductor devices are currently being explored for the amplification of RF signals.
Wide band-gap RF PAs such as those made from silicon carbide (SiC) and gallium nitride (GaN) offer improvements in bandwidth, output power, and efficiency when compared to their narrow band-gap counterparts. However, due to the increased price associated with wide band-gap devices, many mobile device manufacturers continue to rely on conventional RF PAs in the design and manufacture of RF circuitry. While there are many contributing factors to the increased price of wide band-gap semiconductor devices, a large component of the cost is due to the packaging thereof.
FIGS. 1 and 2 show a conventional package 10 for a wide band-gap semiconductor device 12. The conventional package 10 includes a ceramic body 14 and one or more metal contacts 16. Inside the package 10, an air cavity 18 surrounds the wide band-gap semiconductor device 12, which is attached to a metal substrate 20 via a die attach material 22. One or more bond wires 24 couple the wide band-gap semiconductor device 12 to a first metal contact 16A and a second metal contact 16B. The air cavity 18 and the metal substrate 20 dissipate the heat generated by the wide band-gap semiconductor device 12, while simultaneously isolating and protecting the wide band-gap semiconductor device 12 from the outside environment. Although suitable for protecting even a wide band-gap semiconductor device and dispersing the heat generated therefrom, the ceramic body 14 and the metal substrate 20 of the conventional package 10 are expensive to manufacture, thereby driving up the cost of electronics packages including wide band-gap semiconductor devices.